This page is just a reference of all the known Steam APIs, I do not know how they work. Please do not email me with questions.

Creates an async game session

https://partner.steam-api.com/IGameNotificationsService/CreateSession/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 Yes The appid to create the session for.
uint64 Yes Game-specified context value the game can used to associate the session with some object on their backend.
{message} Yes The title of the session to be displayed within each user's list of sessions.
{message} Yes The initial state of all users in the session.
uint64 Nosteamid to make the request on behalf of -- if specified, the user must be in the session and all users being added to the session must be friends with the user.

Deletes an async game session

https://partner.steam-api.com/IGameNotificationsService/DeleteSession/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes The sessionid to delete.
uint32 Yes The appid of the session to delete.
uint64 Nosteamid to make the request on behalf of -- if specified, the user must be in the session.

Deletes a batch of async game sessions

https://partner.steam-api.com/IGameNotificationsService/DeleteSessionBatch/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes The sessionid to delete.
uint32 Yes The appid of the session to delete.

Enumerates a user's sessions

https://partner.steam-api.com/IGameNotificationsService/EnumerateSessionsForApp/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 Yes The sessionid to request details for. Optional. If not specified, all the user's sessions will be returned.
uint64 Yes The user whose sessions are to be enumerated.
bool NoBoolean determining whether the message for all users should be included. Defaults to false.
bool NoBoolean determining whether the message for the authenticated user should be included. Defaults to false.
string NoLanguage to localize the text in.

Get the details for a specific session

https://partner.steam-api.com/IGameNotificationsService/GetSessionDetailsForApp/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
{message} Yes
uint32 Yes The appid for the sessions.
string Yes Language to localize the text in.

Requests that a user receive game notifications for an app

https://partner.steam-api.com/IGameNotificationsService/RequestNotifications/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes The steamid to request notifications for.
uint32 Yes The appid to request notifications for.

Updates a game session

https://partner.steam-api.com/IGameNotificationsService/UpdateSession/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes The sessionid to update.
uint32 Yes The appid of the session to update.
{message} NoThe new title of the session. If not specified, the title will not be changed.
{message} NoA list of users whose state will be updated to reflect the given state. If the users are not already in the session, they will be added to it.
uint64 Nosteamid to make the request on behalf of -- if specified, the user must be in the session and all users being added to the session must be friends with the user.

Creates an async game session

https://api.steampowered.com/IGameNotificationsService/UserCreateSession/v1/
NameValueTypeRequiredDescription
uint32 Yes The appid to create the session for.
uint64 Yes Game-specified context value the game can used to associate the session with some object on their backend.
{message} Yes The title of the session to be displayed within each user's list of sessions.
{message} Yes The initial state of all users in the session.
uint64 Nosteamid to make the request on behalf of -- if specified, the user must be in the session and all users being added to the session must be friends with the user.

Deletes an async game session

https://api.steampowered.com/IGameNotificationsService/UserDeleteSession/v1/
NameValueTypeRequiredDescription
uint64 Yes The sessionid to delete.
uint32 Yes The appid of the session to delete.
uint64 Nosteamid to make the request on behalf of -- if specified, the user must be in the session.

Updates an async game session

https://api.steampowered.com/IGameNotificationsService/UserUpdateSession/v1/
NameValueTypeRequiredDescription
uint64 Yes The sessionid to update.
uint32 Yes The appid of the session to update.
{message} NoThe new title of the session. If not specified, the title will not be changed.
{message} NoA list of users whose state will be updated to reflect the given state. If the users are not already in the session, they will be added to it.
uint64 Nosteamid to make the request on behalf of -- if specified, the user must be in the session and all users being added to the session must be friends with the user.